1. Field of the Invention
The present invention relates, in general, to compositions and methods for dispersing petroleum spills, and for accelerating biodegradation of such petroleum spills, and especially those that have occurred upon a body of water or any other surface.
2. Related Art
Crude petroleums, as well as many products derived from them, are shipped from oil-producing locations to oil-consuming locations in ocean-going vessels having huge capacities. Accidents in which the hulls of such vessels are breached and their contents spilled can cause serious damage to the environment. Unfortunately, such accidents are not at all uncommon. Land and offshore oil wells also can be a source of oil spills into ocean waters. Oil spills from such accidents may quickly spread over many square miles of water surface. When they occur near, or drift to, shorelines, such spills are particularly destructive toward local wildlife and plant life. Petroleum spills of this type also damage boats, fishing gear and harbor installations; and they greatly diminish the value of the shore as a recreational resource. If not treated, such spills require long periods to biodegrade; indeed, about 22 years is required to completely biodegrade one kilogram of crude oil by natural processes.
Other oil spills are the result of deliberate actions such as acts of war, sabotage, and illegal discharge of cleaning fluids that are employed to clean oil tankers in preparation for carrying a petroleum product that differs from the last product carried. Petroleum products flowing through refineries and oil transport pipe systems are often spilled on land as well. Such land spills likewise require very long periods; to biodegrade. Furthermore, since petroleum products are flammable, intense fires often occur as a result of such spills. Such fires are fed by vapors released by the petroleum products, such vapors including, e.g., ammonia and methane vapors. It is therefore highly advantageous to be able to contain and remove oil spills, and to arrest the vapors so that they may not enter and pollute the atmosphere, as soon as possible after the event.
Many methods have been used to remove oil spills from water and/or land. Such methods include physical removal of the petroleum from the water or land chemical remediation of the spilled petroleum through the use of dispersants and so-called “sinking agents,” and, in some cases, intentionally burning floating petroleum slicks. Chemical remediation through the use of liquid, oil dispersant agents is the most frequently employed clean-up method because such liquids can be readily applied to large oil spills and because this method is generally more cost-effective than physical remediation methods.
Most of the more effective methods of chemically remediating oil spills involve the use of various surfactant compositions. A surfactant is a surface-active agent whose molecules are composed of groups of opposing polarity and solubility, i.e., surfactants usually have both an oil-soluble hydrocarbon chain and a water-soluble group. Surfactants can be anionic, cationic or nonionic and they may be comprised of mixtures of any of these types of surfactants. Such surfactant mixtures often include other chemical agents, such as solvents, that enhance the dispersant capabilities of the surfactant. However, not all surfactant compositions are effective in dispersing spilled oil products—and many of the more effective ones have the drawbacks of being toxic and/or not biodegradable.
Oil spill dispersant compositions employing a wide variety of surfactants are found in the patent literature. For example, U.S. Pat. No. 4,597,893 to Byford et al. teaches a dispersant composition for treating oil on water. The composition comprises a nonionic surfactant, an anionic surfactant, a solvent, and water. The nonionic surfactant can be one or more polyalkoxylated (5 to 55 moles) sorbitol or sorbitan fatty acid esters containing 40 moles of ethylene oxide and having a hydrophilic/lipophilic balance (HLB) of 9 to 12. The nonionic surfactant comprises 8 to 58 weight percent of the overall composition. The anionic surfactant is preferably a salt of an alkyl aryl sulfonate. The solvent is a five- to ten-carbon primary alcohol, glycol, or glycol-ether, for example, ethylene glycol monoburyl ether. A water component also may be added as desired.
U.S. Pat. No. 3,793,2118 to Canevari et al. teaches dispersal of oil slicks on water with a dispersant comprising a C10 to C12 aliphatic monocarboxylic acid or sorbitan monoester thereof, a sorbitan monoester polyoxyalkylene adduct, and a dialkyl sulfosuccinate salt. The dispersant can be applied to an oil slick with or without a solvent, such as, for example, paraffin (Isopar). The total hydrophilic/lipophilic balance of these compositions is between 9 and 11.5.
U.S. Pat. No. 4,382,873 to Gatellier et al. teaches a dispersant and biodegradant for oil that has been spilled on water. The dispersant contains (1) an assimilable nitrogen compound derived from melarnine, (2) a hydroxy-providing compound such as a monoalcohol or a mono alkyl derivative of ethylene glycol, (3) an assimilable phosphorus derivative and (4) at least two of the following surface-active agents: sorbitan monolaurate, sorbitan trioleate, sorbitan monooleate, anhydrosorbitol monooleate, an ethoxylated primary alcohol (C12–C13), or PEG (300–400) mono- or di-oleate.
U.S. Pat. No. 3,959,134 to Canevari teaches an oil collection agent that surrounds and collects oil that has been spilled on water. The agent is a mixture of a C10 to C20 saturated or unsaturated fatty acid or the sorbitan monoester thereof (e.g., SPANN), and a nonpolar solvent such as isoparaffin.
U.S. Pat. No. 4,146,470 to Mohan et al. discloses a combination of microorganisms and surfactants to disperse and digest oil slicks. The microorganism is preferably Micrococcus certificans. The surfactant mixture contains 15% to 75% by weight of (1) sorbitan monooleate (SPAN 80) and polyoxyethylene sorbitan monooleate (TWEEN 80), or (2) an alkyl glycoside, or a mixture of (1) and (2). These surfactants may or may not be diluted in a paraffin solvent (Isopar). The HLB of the resulting composition is between 6.9 and 9.5.
There is, however, still a need for improved oil dispersant compositions. This need follows from the fact that many prior art dispersants; (1) are not always effective in dispersing highly viscous crude petroleum spills; (2) employ other components (in addition to nonionic surfactants), e.g., anionic surfactants, solvents, and dialkyl sulfosuccinate salts, that are not readily biodegradable, or contain compounds (e.g., certain anionic surfactants) that are themselves extremely toxic to the environment, and (3) cannot sustain a hydrophilic/lipophilic balance at a level that serves to increase their solubility with water. Others have unacceptably short shelf lives and, hence, must be mixed in the field, and few, if any, are also capable of serving as a fire-fighting agent as well as an oil dispersant.
3. Solution to the Problem.
Several of the above-noted patents show that ethoxylated sorbitol oleates have been used in various dispersants used to treat oil spills; however, many ethoxylated sorbitol oleate-containing dispersants also have proven to be rather unstable and, hence, not well suited for long-term storage and are therefore of rather limited practical utility. Consequently, there have been many attempts to increase the stability of ethoxylated sorbitol oleate-containing oil emulsifying agents by adding other surfactant ingredients such as, for example, primary alcohols to them. However, primary alcohols alone have proved to be rather poor stabilizers for oil dispersants of this kind.
Applicant has, however, discovered that other types of surfactants having the hereinafter-described attributes can be added to certain ethoxylated sorbitol oleate-containing oil-emulsifying agents to form water-miscible compositions that are very effective at emulsifying spilled petroleum and/or petroleum products and are particularly characterized by their long shelf lives and by the fact that they employ only nonionic surfactants that are, in turn, characterized by their relatively low toxicity to the environment and by their relatively fast biodegradability. The emulsifying compositions of the present invention also are capable of remediating oil spills on land as well as on water.
Applicant's emulsifying compositions have other utilities as well. For example, they can be used as fire-fighting agents, and especially against class B (hydrocarbon) fires in addition to class A (natural fuels), class C (electrical), and class D (metals) fires. In particular, whether the target petroleum or petroleum-based product (e.g., oil or fuel) is spilled or burning, the composition of this invention bounds the petroleum into a fine emulsion. In the case of burning petroleum, the composition of this invention encapsulates the petroleum droplets to form an emulsion and prevents escape of vapors that feed the fire, e.g., ammonia and/or methane (which are released by the oil), thereby cutting off the source of and extinguishing the fire. When applied to a petroleum spill, the same emulsion extracts the petroleum from the ground or water surface and is of a nature that readily accelerates the natural biodegradation process of the petroleum while maintaining a very low level of aquatic toxicity. Moreover, the herein-described oil dispersant compositions can be used as cleaning agents in those situations where the surface to be cleaned has a high hydrocarbon concentration, e.g., airport runways and aprons, as well as various container walls, for example, those of rail cars, tanker trucks, sea-going tankers, storage tanks, and automobile fuel tanks. In still other applications, these compositions can be used to maintain and clean oil-contaminated machine tool parts and to maintain the track beds, switches, etc., of railway systems. Applicant's compositions may even be used to accelerate the rate of biodegradation in sewage systems. In addition, tests on live animals have shown that applicant's compositions are also exceptionally effective in the safe cleaning of oil-contaminated wildlife, such as birds, without any observable side effects. Further, applicant's compositions have been independently tested and found acceptable for use as cleaning agents in meat packing and poultry processing plants. As stated earlier herein, the composition of this invention can also be used to prevent the escape of (i.e., suppress) vapors released by petroleum or petroleum-based products, particularly spilled petroleum or petroleum-based products. Such vapors are typically ammonia and/or methane vapors. In addition, the compositions can be used to suppress ammonia and/or methane vapors released at sites containing materials undergoing biodegradation or decay, non-limiting examples of which include, e.g., sites containing petroleum and/or petroleum-based products or other material undergoing biodegradation or decay and releasing ammonia and/or methane vapors, compost (including decaying leaves) piles, animal waste sites, land fills containing petroleum or petroleum-based products or other material undergoing degradation or decay and releasing methane or ammonia vapors, and the like.